This invention relates generally to time delay relays and more particularly to such a relay which is both temperature and voltage compensated.
Time delay relays or switches of the type including an active bimetallic element carrying a contact and arranged for closing and opening with respect to a second contact carrying element in accordance with heat applied to the active bimetallic element by an electrically operated heater coil wrapped thereabout, are well know in the art.
In such heat activated time delay relays, consistent operation thereof may be disrupted because of variations in ambient temperature and voltage variations of the source supplying energy to the heater coil.
In many time delay relays of the type described, ambient temperature compensation is achieved by introducing, as the second contact carrying element, a second bimetallic element which is selected to move with the active bimetallic element as the ambient temperature varies, thus maintaining the contact gap between elements relatively consistent over a wide temperature range; i.e. -40.degree. F. to 180.degree. F. See for example U.S. Pat. Nos., 2,792,533; 2,889,429; 3,601,736 and 3,855,562.
To achieve, from a time delay relay of the aforementioned type, a consistent time delay when voltage applied to the heater coil of the active bimetallic element varies, is more difficult. In this case, either the contact gap between elements may be varied with voltage or the power dissipation in the heater coil may be controlled or regulated in accordance with voltage variations.